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Evolution and the History of
Life
Part 2
MLK
Fall 2005
M.Elizabeth
www.marric.us/teaching
Natural Selection
Darwin theorized that evolution occurs through a
process he called natural selection
Overproduction
1. ______________
– Each species produces
more offspring that will naturally survive.
Genetic Variation – individuals will be
2. ______________
slightly different from one another.
3. ____________
– competition for resources
Survival Struggle
Abiotic and Biotic factors
Successful Reproduction – fitness
4. ___________________
(Survival of the fittest)
Genetic Variation
Two important words:
1. Genotype: The actual genetic code of an
individual’s DNA.
2. Phenotype: The physical characteristics
of an individual.
Genotype versus Phenotype
In many cases the phenotype is dominated
by the genotype.
In other cases, the environment exerts
strong controls on the outward appearance
of an organism. There might be the
genetic potential, but it is not expressed.
Thus, in general the phenotype represents
some combination of genetic and
environmental factors.
Chapter 8.3 Natural Selection in Action
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•
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Insecticide Resistance
Adaptation to Pollution
Formation of New Species
•
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Separation
Adaptation
Division
Insecticide Resistance
• Insects that cause economic or health
damage are becoming more difficult to kill
due to insecticide resistances.
• Insecticides are compounds designed to
kill insects (cidal – to kill).
• Insects that are resistant to a particular
insecticide can survive and reproduce
while those that do not have the genotype
that infers resistance will die and will not
reproduce.
Resistance
• The application of the harmful material (by
humans) results in an artificial selection for those
insects that are resistance.
• The same, unfortunately occurs to disease causing
bacteria and virus, creating “super bugs” which
often times results in incurable situations or
death because antibiotics (against life) are no
longer effective.
• This is why it is so important when prescribed an
antibiotic to complete the treatment to avoid
mutation during treatment of a pathogen creating
a resistant pathogen that can survive – generation
times of bacteria and virus is measured in
minutes.
Adaptation to Pollution
• Peppered moths are the classic case.
• Dark moths were low in population because
they did not blend well with the
environment and so where eaten by
predators. The pale moths were high in
population because they were camouflaged.
• Then comes along the Industrial Revolution
with coal burning to fuel factory machines
and heat homes. The results of burning
coal are sooty smoke, acid rain, and
mercury contamination.
• Well, the sooty smoke coated the
vegetation made those pale moths
stand out like a sore thumb and the
dark moths became camouflaged. So
what do you think happened?
• The population of dark moths
increased and the population of pale
moths decreased.
Match each statement about the peppered moth population
(1-4) with the appropriate step in natural selection (a-d).
B
A
D
C
1. Moths that live to
maturity may mate and
produce offspring.
2. A population of peppered
moths contains some
light-colored moths and
some dark-colored moths.
3. Many moths do not
survive because they are
eaten by birds.
4. Peppered moths lay many
eggs.
a. Genetic
variation
b. Successful
reproduction
c. Overproduction
d. Struggle to
survive
Formation of New Species
Steps: Separation, Adaptation, Division
(speciation).
• Separation allows the gene pool to be
come isolated where no mixing of the
populations occur.
• Adaptation are mutations that help the
species to be successful in the new
environment.
• Division occurs over time these mutant
changes result in a separate species that
cannot interbreed, speciation.
Chapter 8 Review
• One species evolves into another through
speciation
the process of _____________________.
• A group of similar organisms that can mate
with one another to produce fertile
species
offspring is known as ________________.
adaptation helps an organism
• A(n) __________
survive better it its environment.
Evolution
• ____________is
the process by which
populations change over time
•
•
•
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Artificial selection
In ______________________________,
humans select traits that will be passed from
one generation to another.
A change in a gene at the DNA level is called a
Mutation
__________________.
The theory of evolution combines the
Natural selection and
principles of _________________________
genetic inheritance
__________________.
The fact that all organisms have DNA as their
genetic material is evidence that all organisms
desended__________________________.
from a common ancestor.
______
Everything had to start somewhere.